Fin forming devices



9, 1955 R. M. STIKELEATHER 3,216,232

FIN FORMING DEVICES Original Filed Oct. 12, 1950 4 Sheets-Sheet lINVENTOR. flaw 11. 6%

BY zwaw J;

Nov. 9, 1965 Original Filed Oct.

R. M. STIKELEATHER FIN FORMING DEVICES 4 Sheets-Sheet 2 INVENTOR. KM M.SW

9, 1955 R. M. STIKELEATHER 3,216,232

FIN FORMING DEVICES 4 Sheets-Sheet 3 Original Filed Oct. 12, 1950INVENTOR. RM M. 5M

1955 R. M. STIKELEATHER 3,216,232

FIN FORMING DEVICES 4-Sheets-Sheet 4 Original Filed Oct. 12, 1950 H NIHH /"l INVENTOR. KM 5% United States Patent 3,216,232 FIN FORMING DEVICESRobert M. Stikeleather, Holbrook, Mass., assignor to AerofinCorporation, Syracuse, N.Y., a corporation of New Jersey Continuation ofapplication Ser. No. 433,601, June 1, 1954, which is a division ofapplication Ser. No. 189,854, Oct. 12, 1950, now Patent No. 2,713,375,dated July 19, 1955. This application Nov. 28, 1960, Ser. No. 76,435

3 Claims. (Cl. 72-100) This invention relates to the production of heatexchanger tubing with closely spaced spiral or helical fins, and toapparatus for forming same.

This application is a continuation of co-pending application S.N.433,601, filed June 1, 1954, now abandoned, which Was a division ofco-pending application S.N. 189,- 854, filed October 12, 1950, and nowPatent No. 2,713,- 375, issued on July 19, 1955.

As disclosed in the aforementioned applications, a machine is providedfor forming a spiral or helical fin on a tube, and more particularlymeans permitting the application of a smooth spirally wound fin about atube in such manner as to cause the fins to adhere to the tube surface.

A successful form of heat exchanger for conditioning air or other gasesis a tube through which a heat exchange fluid is circulated, having ametal ribbon wound spirally on its exterior surface and serving as anextended heat exchange surface. Such ribbons on such tubes are usuallyreferred to as fins.

Prior methods of forming closely spaced fins spirally on tubes haveinvolved either crimping the inner edge of a ribbon to cause it to curlaround the tube, or forming the ribbon into a spiral before it is placedon a tube. Crimped fins are not suitable for some types of heatexchangers where smooth fins are preferred due to their lower resistanceto gas flow. Pre-forming a spiral provides a smoth fin, but placing itsatisfactorily on a tube for proper spacing and tension is troublesome.

This invention departs from prior practices by rolling a smooth ribbonor wire directly upon a tube so as to wind spirally thereon and formspaced fins When the tube is rotated and advanced. This is accomplishedby deforming the ribbon so that its thickness is less at the outer edgethan at its inner edge. Deforming the ribbon in this manner causes anincrease in the length of the outer edge of the ribbon thereby causingit to curl tightly around the tube.

In one embodiment of the invention, a ribbon is fed between two rolls,one having a plane backing-up surface, and the other having a beveledsurface shaped to form the ribbon as it passes between the rolls.Preferably, the roll having the plane surface is a disk roll having anouter flange which extends between the fin being formed and the adjacentpreviously formed fin. The roll having the beveled surface preferablyhas such a small diameter compared to the disk roll, that the pressureit exerts rolling the ribbon is not suflicient to break the disk.

In prior fin winding machines, great difficulty was encountered incoordinating the formation of a ribbon into a spiral, and the advanceand rotation of a tube upon which the ribbon was applied, resulting inimproper spacing of the turns of the fin, and in irregularities in thetension of the ribbon.

A feature of this invention resides in providing means for advancing androtating a tube upon which a ribbon is being wound, which is socoordinated with the tension of the ribbon as it is placed upon thetube, that such means slips continuously around the tube, its rate ofslip increasing when the tension of the ribbon increases above normal,and its rate of slip decreasing when the tension on the ribbon decreasesbelow normal; thus, the proper tension is maintained at all times on theribbon so that it cannot become loose on the tube, nor become too tightso as to break or become distorted.

A feature of this invention resides in providing a relatively largeflanged roll and a relatively small beveled roll which cooperates withthe flange of the flanged roll for deforming the outer portion of aribbon for causing it to curl about a tube, and in providing arelatively large backing-up roll against the beveled roll opposite theflanged roll. The flanged roll has a relatively large diameter forproviding minimum difference between its rotational pressure against theinner and outer deformed portions of the ribbon, and it has a relativelythin flange for passage between the first and second convolutions of thefin being formed. By using a relatively small beveled roll, the pressureagainst the flange of the flanged roll is substantially smaller than ifa large beveled roll was used, permitting the flange of the flanged rollto be thin enough to pass between adjacent closely spaced fins. Thesmall beveled roll has insufficient strength in itself to withstand thepressure involved in deforming the ribbon so that the large backing-uproll is used to prevent damage to the beveled roll.

Prior machines of this general type have employed beveled rolls havingsubstantially the same diameters as the flanged rolls, requiring verythick flanges for withstanding the great pressures against them. Suchthick flanges prevented the fin being wound from being closely spaced.

As the fin passes from between the forming rolls, if very thin stock isused, it may have a wave formed therein which is undesirable wheresmooth fins are preferred. A straightening roll is provided for removingthis wave.

An object of the invention is to provide an improved method of forming ametal fin spirally about a metal tube.

Another object of the invention is to provide an improved machine forforming a metal fin spirally about a metal tube.

Another object of the invention is to coordinate the advance androtation of a tube upon which a ribbon is wound with the tension of theribbon.

The attached drawings illustrate a preferred embodiment of my invention,in which FIGURE 1 is a plan view of a fin winding machine embodying theinvention;

FIGURE 2 is a view in front elevation of the machine shown in FIGURE 1;

FIGURE 3 is an enlarged sectional view taken along the line III-III ofFIGURE 1;

FIGURE 4 is a plan view of the portion of the machine shown in FIGURE 3;

FIGURE 5 is an enlarged view, partly in plan and partly in section, ofthe left-hand end of the machine shown in FIGURE 1, having thestraightening disk assembly omitted;

FIGURE 6 is an enlarged end view, with the end plate removed, of theassembly for rotating and advancing a tube upon which a ribbon is to bewound;

FIGURE 7 is a sectional view taken along the line VIIVII of FIGURE 6;

FIGURE 8 is a plan view of the head assembly shown in FIGURE 6, havingthe upper portion of the housing of the assembly removed; and

FIGURE 9 is a fragmentary view, partly in elevation and partly insection, of the forming rolls and of several turns of a spiral finformed thereby on a tube.

Referring to the attached drawings, there is shown the fin formingmachine of the present invention. Such machine includes uprights 20which support a lower table 21 and an upper table 22. A head 23 forrotating and advancing a tube 24, on which a fin is to be applied, isbolted to an upstanding annular flange formin one end of the bearinghousing 25. Shaft 26 in head 23 has the head member 27 formed on itsinner end (refer to FIG- URE 7) and has pulley 28 attached to its outerend. Pulley 28 is driven through belt 29 by pulley 30 on shaft 32. Thegeared-down electric motor 33, bolted to the underside of table 22,rotates shaft 32 through a pulley 31 attached thereto. Belting 34connects pulley 31 and motor 33. Shaft 32 extends through a bearing 35supported on table 21 and is connected through an over-running clutch 36with an aligned shaft 37 which extends through bearing 38 to coupling 39which connects it to an aligned shaft 40 carrying pulley 31.

Belt 42 connects pulley 41 with pulley 43 which drives, through a slipjoint 44, a straightening disk assembly indicated generally at 45.

Shaft 40 extends into one side of gear box 46. Vertical shaft 47 extendsfrom the upper end of gear box 46. Preferably, the upper end of shaft 47is tapered inwardly at its upper end (refer to FIGURE 3) to provide a taered roll 48 which cooperates with disk roll 49 to roll the outer edgeof a ribbon so that it has less thickness at its tip than at its heel.It will be appreciated that roll 48 has a diameter only a fraction ofthe diameter of disk roll 49, preferably less than one-half the diameterof the disk roll as shown in FIG. 9.

A backing roll 50 of greater diameter than forming roll 48 provides linecontact with the upper end of shaft 47 adjacent the forming roll 48thereon and provides backing-up support for the shaft during the finningoperation. Since roll 48 is of very small diameter to permit a spiralhaving an extremely small diameter to be formed, it is necessary toprovide roll 50 to assure the necessary strength. If roll 50 were notprovided, roll 48 could not provide adequate pressure to form a spiralof extremely small diameter. Roll 50 is held in fixed position axiallyof the machine by a pin 51, but is free to rotate about pin 51 by itscontact with shaft 47. As stated above, roll 50 permits the applicationof the necessary pressure by roll 48 to the metal ribbon to roll in theribbon about the tube to form a fin of desired contour.

Disk roll 49 terminates in a flange 52 adjacent the tapered roll 48. Theend of disk roll 49 is plane and is in contact with the ribbon, ashereinafter described.

A shaft 53 aligned with shaft 40, extends from the opposite end of gearbox 46 and has attached thereto a relatively small sprocket 54 which isconnected by a chain 55 to a relatively large upper sprocket 56 mountedon shaft 57 which supports disk roll 49, thus rotating disk roll 49 atreduced speeds. It is desirable to rotate the disk roll 49 at start-upto aid in feeding ribbon into the nip formed between rolls 48 and 49.

Shaft 53 also has attached thereto a pulley 58 connected by belting 59to a pulley 60 attached to the hydraulic clutch member 61 whichcooperates with a similar clutch member 62, driven by electric motor 63.The motor 63 and clutch members 61 and 62 are contained in a housing 64which has a partition 65 separating the motor and the clutch members forisolating the motor from the fluid in which the clutch members operate.

The geared-down motor 33 is used for rotating the rotary mechanismdescribed in the foregoing at low speed, for starting up, and motor 63is provided for driving the assembly at high speed after the start ofthe fin winding operation.

In FIGURES 1, 3, and 4 there is shown a ribbon 70 which is fed betweenroller bearings 71 supported by a horizontal guide plate 72. The upperand lower edges of ribbon 70 are in contact with rollers 73 which arejournalled in the vertical guide plate 74. The ribbon 70 then passesunder rolls 75 journalled in plate 74, adjacent vertical guide 75', andpasses between the forming roll 48 and disk roll 49, as illustrated alsoin FIGURE 9.

It will be understood one or more rolls 75 may be employed to guide theribbon into the nip of rolls 48 and 49.

The means for rotating and advancing the tube 24 on which a fin is to beformed will now be described with reference to FIGURES 6, 7 and 8 of thedrawings. The head member 27 on the inner end of the shaft 26 hasattached thereto the supports 123 in the inner ends of which arejournalled the inner ends of the shafts 76 and 77, the outer ends ofwhich are journalled in the head member 27. On the inner ends of theshafts 76 and 77 are attached the gears 78 and 79 respectively, whichintermesh with the inner gear 80, which is held against rotation withrespect to the cover plate 120 by the pins 120'. The shafts 76 and 77have attached thereto between their ends the worm gears 81 and 82respectively.

The two oppositely positioned counter-weights 91 have the shafts 84 and87 journalled for rotation therein adjacent their inner ends. Thecounter-weights are pivoted for rotation about the two pivot shafts 90which extend through the two oppositely positioned supports 121 whichare secured at their outer ends to the face plate 27.

The gear 83 meshing with the worm gear 82 is attached to the shaft 84adjacent one end thereof, the tube feed roll 85 being attached to theshaft 84- adjacent the other end thereof. The collar 84' is attached tothe end of the shaft 84 adjacent to roll 85. The gear 86 meshing withthe worm gear 81 is attached to the shaft 87 adjacent one end thereof.The collar 87 is attached to the end of the shaft 87 adjacent to roll88.

The ends of the counter-weight 91 are interconnected by the coiledsprings 89 which pull the rolls 85 and 88 towards each other infrictional contact with the tube 24. The feed rolls 85 and 88 havesurfaces curbed to fit the exterior surface of the tube 24.

The pivoted counter-weights 91 oppose the action of centrifugal force intending to cause the rolls 85 and 88 and the gears 83 and 86 to moveoutwardly. This may be understood by reference to FIGURE 7 where it willbe seen that centrifugal force will cause the larger, verticallyextending portions of the counter-weights to tend to move outwardly andto rotate about the pivots 90 towards the rolls 85 and 88, thus tendingto cause the rolls 85 and 88 and the gears 83 and 86 to move inwardly inopposition to the action of centrifugal force acting on such rolls andgears. The pivoted counter-weights permit the advancing and turningrolls 85 and 88 to move inwardly or outwardly against the tension of thesprings 89 as the tube 24 varies in size.

In the operation of the tube rotating and advancing mechanism therotation of shaft 26, as described above, causes rotation of the headmember 27. The gears 78 and 79 carried by shafts 76 and 77 are caused torotate though being meshed with the fixed gear attached to the head 23.This causes rotation of shafts 76 and 77 and rotation of the worms 81and 82. Rotation of the worms 81 and 82 rotates worm gears 83 and 86whiEh rotate the shafts 84 and 87 respectively. Tube feed rolls and 88,mounted on shafts 84 and 86 are rotated in a direction to advance thetube 24 toward the fin forming rolls, to the left considering FIGURE 7of the drawing. At the same time since the head member 27 is rotated,the rolls 85 and 88 are rotated bodily about the axis of the tube 24causing the tube to rotate.

Springs 89 are tensioned so that under operating conditions the frictionbetween the rolls 85 and 88 is sufficient to cause about 10% slippagebetween the tube and the rolls 85 and 88 under normal ribbon tension. Ifthe ribbon tension increases above normal, the tube will be held back acorresponding amount through its connection thereto so that increasedslippage will occur. If the ribbon tension decreases below normal, itspull on the tube will decrease a corresponding amount so that decreasedslippage will occur. It will be appreciated that the amount of slippageis empirically determined; slippage within a wide range may occur. Ihave found that as much as 50% slippage may occur, if desired.

As the tube 24 is rotated and advanced as described, and the ribbon 70is fed between the rolls 48 and 49 as described, the outer edge of theribbon is squeezed between the rolls so that its width is less than thewidth of the inner edge. This causes the ribbon to curl around the tubeso that its inner edge or heel grips the tube tightly, forming a spiralfin thereon, as illustrated in FIGURES 3, 4, and 9 of the drawings. Theflange 52 of roll 49 passes between adjacent turns of the fin as it isformed and supports and aids in spacing the fins. It will be appreciatedthe thickness of the flange of roll 49 is material in my invention. Suchthickness preferably is in the order of the desired spacing betweenfins, or may be smaller. It will be appreciated such thickness may beslightly greater than the spacing between adjacent fins, provided suchthickness is not so great as to loosen the fin upon the tube. Any slightdistortion of the fin caused by such thickness will be eliminated bypassage through the straightening device 45.

It will be appreciated that rotation of rolls 48 and 49 draws the ribbonfrom supply and rolls it in about tube 24, frictionally securing theribbon to the tube without substantial deformation at the heel andelongating the tip longitudinally of the ribbon to wind or curl theribbon about the tube spirally to form the fin. The pressure exerted bythe small forming roll 48 in rolling and forming the fin about the diskroll 49 is taken by backing roll 50. In other words, roll 48 in itselfneed not exert the pressure required to shape and wrap the ribbon sothat it may be small enough to roll the ribbon and not exert a pressurein excess of the strength of the disk.

As the fin passes from between rolls 48 and 49, it may have a wavetherein which for some duties would be undesirable so that thestraightening disk assembly 45 is provided for removing this wave.

At the start of a fin winding operation, the straightening disk assembly45 is pivoted out of position; after the advancing end of a ribbon hasbeen placed by hand at the ribbon entering edges of the forming rolls,the motor 33 is started. This rotates the tube advancing and rotatingmechanism and the forming rolls at slow speed for enabling any necessaryadjustment to be made. At this time motor 63 is not energized. When afew turns of the fin have been properly formed, the straightening diskmechanism is rotated to its operating position, and the motor 63 isstarted. It starts at high speed and for preventing any sudden strain onthe fin forming mechanism, the fluid clutch comprising members 61 and62, is provided. Since the clutch 36 is over-running, the motor 33provides no drag at this time and may be shut down.

It may be desired to employ the machine of the present invention to forma fin with a crimp or other indentation in the tip rather than to form asmooth fin. In such circumstances the straightener assembly 45 may beomitted or operated at the same peripheral speed as the fin so that theescalloped disk will form crimps in the outer edge of the fin. Anysuitable device may be substituted for the straightening disk to formthe desired contour.

It will be appreciated, as shown in FIGURES 1 and 2, the straighteningassembly 45 is adjustable axially by means of threaded shaft 124 of thetube 24 as well as being rotatable to and from tube 24. Under somecircumstances, it may be possible to operate the machine satisfactorilywithout employing the straightening assembly 45. This is generallyundesirable, however, since very delicate adjustment of the machine isrequired. For commercial operation, it is generally preferable to employthe straightening assembly.

If desired, the metal ribbon 70 may be lubricated prior to its supply tothe forming roll. In most cases, however,

such lubrication is not necessary. While the fin is frictionally securedto the tube, under some circumstances, it may be desirable to solder thefin to the tube. In such case, any suitable soldering arrangement may beemployed.

The present invention provides a speedy, economical device for forming asmooth surface fin about a metal tube. Preferably, in most cases aseparate head is provided for each diameter of tube to be provided withextended heat exchange surface since the expense of such heads is notgreat.

The present machine permits a fin having any desired thickness to beformed on a tube even a tip thickness as low as three thousandths of aninch. Commercially, the finned tube may have a tipped thickness of fouror five thousandths of an inch. By so forming the tip of the fin, largeamounts of material can be saved in the outer edge of the fin. Thepossible saving may be 20% or more of the cost of the material requiredto form a fin.

While I have described a preferred embodiment of the invention, it willbe understood the invention is not limited thereto since it may beotherwise embodied within the scope of the following claims.

What is claimed is:

1. In a machine for forming a spirally wound fin about a tube, means forfeeding and rotating a tube through the machine, means for feeding sheetmetal stock under tension to an assembly of fin fabricating rolls, saidassembly forming a succession of spirally wound fins about the tube asit advances through the machine, said assembly including a disc rollwith a plane surface and an outer flange which extends between the finbeing formed and the adjacent previously formed fin, a beveled formingroll cooperating with said disc roll and between which the sheet metalstock is engaged, said forming roll having a diameter less than halfthat of the diameter of the disc roll, a back roll rotating against theforming roll on a side thereof opposed to the disc roll, the pressureexerted by the beveled forming roll being resisted by said back roll sothat the disc roll will not be injured despite great pressures exertedthereon by the beveled forming roll, said means for advancing androtating the tube upon which the ribbon is formed being operativeresponsive to the tension of the ribbon as it is placed upon the tube sothat said means continuously slips, with respect to the tube.

2. In a machine according to claim 1, said forming roll having, abeveled nose end, the sheet metal stockbeing formed between the nose endand the disc roll, the disc roll having a peripheral flange slightlyless in thickness than the desired spacing between adjacent fins, saidback roll being in pressure contact with the forming roll.

3. In a machine according to claim 1, the axis of the forming roll beingperpendicular to the axis of the disc roll.

References Cited by the Examiner UNITED STATES PATENTS 760,448 5/ 04Gustavsen. 1,850,936 3/32 Lane et al. 153-64.5 1,896,350 2/33 Bundy153-645 2,353,290 7/44 Bennewitz -38 X 2,601,792 7/52 Dahlstrom 80382,669,012 2/54 Bruegger 29157.3 2,779,383 1/57 Johnson 15364.5 2,792,0505/57 Edwards 153-1645 2,956,335 10/60 Matheny et a1 29157'.3

CHARLES W. LANHAM, Primary Examiner.

WHITMORE A. WILTZ, WILLIAM J. STEPHENSON,

Examiners.

1. IN A MACHINE FOR FORMING A SPIRALLY WOUND FIN ABOUT A TUBE, MEANS FORFEEDING AND ROTATING A TUBE THROUGH THE MACHINE, MEANS FOR FEEDING SHEETMETAL STOCK UNDER TENSION TO AN ASSEMBLY OF FIN FABRICATING ROLLS, SAIDASSEMBLY FORMING A SUCCESSION OF SPIRALLY WOUND FINS ABOUT THE TUBE ASIT ADVANCES THROUGH THE MACHINE, SAID ASSEMBLY INCLUDING A DISC ROLLWITH A PLANE SURFACE AND AN OUTER FLANGE WHICH EXTENDS BETWEEN THE FINBEING FORMED AND THE ADJACENT PREVIOUSLY FORMED FIN, A BEVELED FORMINGROLL COOPERATING WITH SAID DISC ROLL AND BETWEEN WHICH THE SHEET METALSTOCK IS ENGAGED, SAID FORMING ROLL HAVING A DIAMETER LESS THAN HALFTHAT OF THE DIAMETER OF THE DISC ROLL, A BACK ROLL ROTATING AGAINST THEFORMING ROLL ON A SIDE THEREOF OPPOSED TO THE DISC ROLL, THE PRESSUREEXERTED BY THE BEVELED FORMING ROLL BEING RESISTED BY SAID BACK ROLL SOTHAT THE DISC ROLL WILL NOT BE INJURED DESPITE GREAT PRESSURES EXERTEDTHEREON BY THE BEVELED FORMING ROLL, SAID MEANS FOR ADVANCING ANDROTATING THE TUBE UPON WHICH THE RIBBON IS FORMED BEING OPERATIVERESPONSIVE TO THE TENSION OF THE RIBBON AS IT IS PLACED UPON THE TUBE SOTHAT SAID MEANS CONTINUOUSLY SLIPS, WITH RESPECT TO THE TUBE.